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Examining the effects of prey type and water temperature on the feeding behavior of a benthic generalist mesopredator, the California two-spot octopus (Octopus bimaculoides)


Coleoid cephalopods (squids, octopuses, and cuttlefish) have been widely studied for a diversity of scientific inquiries. Despite their relevance as model organisms to fields such as cognitive psychology, neuroethology and physiology, there is still much to be learned about their own biology and how they interact with their environment. One group in particular, nearshore benthic octopuses, occupy an important ecological role as mid-level predators who are also a food resource to a myriad of other predators. Octopuses are generalist carnivores consuming a wide range of prey. They are also poikilotherms and are therefore physiologically sensitive to changes in their physical environment. However, little is known about how biotic and abiotic factors—such as prey type and water temperature—influence their complex suite of feeding behaviors. To investigate the effects of prey type and acute changes in water temperature on prey search, capture, and handling, I conducted controlled feeding trials with the California two-spot octopus (Octopus bimaculoides) and analyzed the videos to extract an integrative combination of behavioral measures and attack kinematics. In Chapter 1, I presented each octopus with either a live crab or live clam, to assess the behavioral variation associated with the characteristics of two distinct prey types. In clam trials, octopuses were less hesitant to approach or touch the prey, but conducted slower attacks, whereas while octopuses were more initially hesitant in crab trials their attacks on crab prey were more dynamic and deliberate. Prey type did not affect octopuses body orientation, arm usage, or eye choice. I also describe an interesting locomotion pattern for these octopuses where they move in a sinusoidal path along the bottom of the tank immediately prior to the attack of a crab, in an apparent corralling of the more mobile prey. For Chapter 2, I studied the effects of acute temperature change at three different treatment levels (baseline (14-17 °C), 20 °C, and 23 °C) on the feeding behavior of O. bimaculoides on live crab prey. I found that temperature had a significant negative effect on the probability that an octopus would attack their prey occurring in the feeding trial, and that warmer water produced longer latency to make an initial movement during the commencement of a trial, slower attack velocity and acceleration, and longer prey handling time. Finally, I discuss the ecological implications of my findings, and how these kinds of changes to octopus predator-prey dynamics could scale up to have system-level impacts.

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